Nate painted the ceiling a vibrant green. "People are like, 'Oh my ceiling has to be white'—it really doesn't," he says. (image and quote source)Here's a lovely, subtle one from Domino magazine
Of course, you can get super fancy, and take ceiling colors to the next level, like this:
Or this... (and yes, this is just painted to -look- like a window and sky)
If you were to go for a colored ceiling, what hue would it be? Anyone actually paint his or her ceilings something other than white?